Figure 6.

Changes in electron-transport activities in isolated thylakoid membranes during incubation in the presence and absence of sorbitol. Thylakoid membranes at a Chl concentration of 10 μg mL⁻¹ were incubated at 32°C in darkness in the presence of 1.0 m sorbitol and in its absence. At designated times, a portion of each suspension of membranes was withdrawn and the activities of PSII and PSI were determined. A, The transport of electrons by PSII from water to DCIP (○, ●) and from DPC to DCIP (▵, ▴) was monitored by following the light-induced reduction of DCIP after the addition of 0.1 mm DCIP and of 0.1 mm DCIP plus 0.5 mm DPC, respectively. B, The transport of electrons by PSI from the reduced form of DCIP to MV was monitored by following the light-induced uptake of oxygen after addition of 15 μm DCMU, 0.1 mm DCIP, 5 mm ascorbate, and 0.1 mm MV to the suspension. Black symbols, In the presence of 1.0 m sorbitol; white symbols, in the absence of sorbitol. Each point represents the average with se of results from three independent experiments.